In April 2020, it was reported that Clairo had begun work on her follow-up to Immunity when she shared a screenshot of a playlist titled 'Album 2 (demos so far)'.

[5] In the writing process, Clairo admitted that "Joanie, my dog, opened up my world in ways I didn't think were capable.

[10] Prior to the announcement of Sling, Clairo provided background vocals on Lorde's song "Solar Power" alongside Phoebe Bridgers.

On June 11, 2021, Clairo released the lead single of the album, "Blouse", which features background vocals from Lorde.

[19] "Blouse" has been described as a folk tune and "crushing ballad" where Clairo sings over a "hushed acoustic guitar" as well as "orchestral swings".

[23] The Line of Best Fit writer Jay Singh described the record to contain relatable themes like "yearning for stability, grappling with our mortality, and striving to treat ourselves with care".